Implicitly smooth a triangular mesh — vcg

Applies smoothing algorithms on a triangular mesh.

Usage

vcg_smooth_implicit(
  mesh,
  lambda = 0.2,
  use_mass_matrix = TRUE,
  fix_border = FALSE,
  use_cot_weight = FALSE,
  degree = 1L,
  laplacian_weight = 1
)

vcg_smooth_explicit(
  mesh,
  type = c("taubin", "laplace", "HClaplace", "fujiLaplace", "angWeight",
    "surfPreserveLaplace"),
  iteration = 10,
  lambda = 0.5,
  mu = -0.53,
  delta = 0.1
)

Arguments

mesh: triangular mesh stored as object of class 'mesh3d'.
lambda: In vcg_smooth_implicit, the amount of smoothness, useful only if use_mass_matrix is TRUE; default is 0.2. In vcg_smooth_explicit, parameter for 'taubin' smoothing.
use_mass_matrix: logical: whether to use mass matrix to keep the mesh close to its original position (weighted per area distributed on vertices); default is TRUE
fix_border: logical: whether to fix the border vertices of the mesh; default is FALSE
use_cot_weight: logical: whether to use cotangent weight; default is FALSE (using uniform 'Laplacian')
degree: integer: degrees of 'Laplacian'; default is 1
laplacian_weight: numeric: weight when use_cot_weight is FALSE; default is 1.0
type: method name of explicit smooth, choices are 'taubin', 'laplace', 'HClaplace', 'fujiLaplace', 'angWeight', 'surfPreserveLaplace'.
iteration: number of iterations
mu: parameter for 'taubin' explicit smoothing.
delta: parameter for scale-dependent 'Laplacian' smoothing or maximum allowed angle (in 'Radian') for deviation between surface preserving 'Laplacian'.

Value

An object of class "mesh3d" with:

vb: vertex coordinates
normals: vertex normal vectors
it: triangular face index

Coercing Surface Inputs

The surface objects are converted to 'mesh3d' object before applying further calculations.

When surface is a surface ieegio object, the returned mesh3d$vb contains vertices that have been left-multiplied by surface$geometry$transforms[[1]] (the first transform stored in the geometry, typically the ScannerAnat or voxel-to-world transform).

Breaking change: Earlier versions (before 0.2.6) of ravetools returned the raw surface$geometry$vertices without applying any transform, so downstream code often multiplied by surface$geometry$transforms[[1]] (or an equivalent) manually before working in world space. Such code will now double apply the transform and produce incorrect coordinates. If you previously applied a transform from surface$geometry$transforms by hand after calling a ravetools mesh function on an 'ieegio_surface', remove that manual step.

Surfaces with an empty or missing geometry$transforms list (for example, surfaces produced by ieegio's volume_to_surface, which stores an identity transform) are unaffected.

If geometry$transforms contains multiple transforms targeting different coordinate spaces, only the first one is used. Callers that need a specific target space should select and apply that transform themselves before calling ravetools mesh functions.

Examples


if(is_not_cran()) {

# Prepare mesh with no normals
data("left_hippocampus_mask")

# Grow 2mm on each direction to fill holes
volume <- grow_volume(left_hippocampus_mask, 2)

# Initial mesh
mesh <- vcg_isosurface(volume)

# Start: examples
rgl_view({
  rgl_call("mfrow3d", 2, 4)
  rgl_call("title3d", "Naive ISOSurface")
  rgl_call("shade3d", mesh, col = 2)

  rgl_call("next3d")
  rgl_call("title3d", "Implicit Smooth")
  rgl_call("shade3d", col = 2,
           x = vcg_smooth_implicit(mesh, degree = 2))

  rgl_call("next3d")
  rgl_call("title3d", "Explicit Smooth - taubin")
  rgl_call("shade3d", col = 2,
           x = vcg_smooth_explicit(mesh, "taubin"))

  rgl_call("next3d")
  rgl_call("title3d", "Explicit Smooth - laplace")
  rgl_call("shade3d", col = 2,
           x = vcg_smooth_explicit(mesh, "laplace"))

  rgl_call("next3d")
  rgl_call("title3d", "Explicit Smooth - angWeight")
  rgl_call("shade3d", col = 2,
           x = vcg_smooth_explicit(mesh, "angWeight"))

  rgl_call("next3d")
  rgl_call("title3d", "Explicit Smooth - HClaplace")
  rgl_call("shade3d", col = 2,
           x = vcg_smooth_explicit(mesh, "HClaplace"))

  rgl_call("next3d")
  rgl_call("title3d", "Explicit Smooth - fujiLaplace")
  rgl_call("shade3d", col = 2,
           x = vcg_smooth_explicit(mesh, "fujiLaplace"))

  rgl_call("next3d")
  rgl_call("title3d", "Explicit Smooth - surfPreserveLaplace")
  rgl_call("shade3d", col = 2,
           x = vcg_smooth_explicit(mesh, "surfPreserveLaplace"))
})

}
#> Package `rgl` is not installed. Please install `rgl` to use this function.
#> Error in loadNamespace(name): there is no package called ‘rgl’